CN114829331B - Method and system for monitoring the flammability of different streams during the production of vinyl acetate - Google Patents

Method and system for monitoring the flammability of different streams during the production of vinyl acetate Download PDF

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CN114829331B
CN114829331B CN202080087055.4A CN202080087055A CN114829331B CN 114829331 B CN114829331 B CN 114829331B CN 202080087055 A CN202080087055 A CN 202080087055A CN 114829331 B CN114829331 B CN 114829331B
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flammability limit
vinyl acetate
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interaction
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CN114829331A (en
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S·R·亚历山大
K·C·汉克斯
S·索梅维勒
D·S·C·李
C·P·德芙琳
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Celanese International Corp
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/04—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds
    • C07C67/05—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides onto unsaturated carbon-to-carbon bonds with oxidation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J12/00—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor
    • B01J12/005—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor carried out at high temperatures, e.g. by pyrolysis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J12/00—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor
    • B01J12/007—Chemical processes in general for reacting gaseous media with gaseous media; Apparatus specially adapted therefor in the presence of catalytically active bodies, e.g. porous plates
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
    • C07C69/02—Esters of acyclic saturated monocarboxylic acids having the carboxyl group bound to an acyclic carbon atom or to hydrogen
    • C07C69/12—Acetic acid esters
    • C07C69/14—Acetic acid esters of monohydroxylic compounds
    • C07C69/145—Acetic acid esters of monohydroxylic compounds of unsaturated alcohols
    • C07C69/15—Vinyl acetate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
    • B01J2208/00008—Controlling the process
    • B01J2208/00628—Controlling the composition of the reactive mixture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00245—Avoiding undesirable reactions or side-effects

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  • Chemical Kinetics & Catalysis (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

Methods and systems for producing vinyl acetate may use a Flammability Limit (FL) equation with improved efficiency at more than one location in a vinyl acetate production process. Wherein FL can be used at one or more of the four parts of the vinyl acetate production process: a reactor, a heat exchanger between the processes, a carbon dioxide removal system, and an ethylene recovery system. Such FL is a function of operating conditions and includes at least one interaction term that represents the interrelationship of two or more operating conditions (e.g., temperature, pressure, and component concentration) on the FL.

Description

Method and system for monitoring the flammability of different streams during the production of vinyl acetate
Priority claim
The present invention claims priority from U.S. provisional patent application 62/950264 filed on day 19, 12, 2019.
Background
The present invention relates to a method and system for producing vinyl acetate.
Vinyl acetate is conventionally produced via the vapor phase reaction of ethylene, oxygen and acetic acid, wherein the ethylene undergoes acetoxylation. The reaction is usually carried out in a fixed bed catalyst reactor. The catalyst may comprise palladium or a palladium/gold mixture supported on silica or alumina matrix. In addition to the formation of vinyl acetate, undesirable combustion of ethylene to form carbon dioxide and water also occurs. Other undesirable impurities that may form include acetaldehyde, ethyl acetate, methyl acetate, acetone, ethylene glycol diacetate, acrolein, and crotonaldehyde.
The selectivity and conversion involved in this reaction are a function of several variables, including reactor temperature, component concentration, and catalyst conditions. Deactivation of the catalyst, which typically occurs over time due to aggregation of tar and polymeric materials on the catalyst surface and/or structural changes of the catalyst metal, can adversely affect the reaction process, particularly with respect to selectivity. These changes in reactor performance ultimately result in a change in the composition of the liquid stream entering the purge zone of the vinyl acetate plant.
Acetoxylation of ethylene produces a crude vinyl acetate product comprising vinyl acetate, water and carbon dioxide, and unreacted ethylene and acetic acid, which are used in excess. Ethylene and acetic acid are recycled back to the reactor from the reaction and purification zone of the plant. The product vinyl acetate is recovered and purified in a purification zone and sent to a holding tank. The wastewater is sent to a treatment facility and carbon dioxide is discharged to a pollution control device. Inert gases such as nitrogen and argon may accumulate over time and thus may be purged from the reaction zone to minimize accumulation.
Generally, the rate of acetoxylation increases with increasing oxygen concentration in the reactor. However, the amount of oxygen that can be introduced into the reactor is limited by the flammability limit of the reaction mixture. The flammability limit is generally defined as the lowest concentration of oxygen in the mixture that will result in an increase in pressure when it contacts the ignition source. If the oxygen concentration exceeds the flammability limit, a fire or explosion may occur.
Various steps have been taken to minimize the risk of such fires or explosions. For example, in the fixed bed reactor of EP0845453, the concentration of oxygen in the inlet gas composition is closely monitored and maintained at or near a threshold value. Mathematical approximations for defining this threshold are described in EP0845453, which is incorporated herein by reference. When the inlet oxygen concentration exceeds the threshold, a shut-down signal is activated and the reaction is ended by shutting down fresh oxygen into the reactor.
However, conventional calculation of flammability limits and/or establishment of non-flammability ranges may be inherently inaccurate. Conventional experimental techniques and methods for developing mathematical relationships typically calculate low flammability limits. These relationships provide a cushion to the true flammability limit. Although safety is achieved, the efficiency of the reaction suffers because it operates at lower oxygen concentrations than indicated by the true flammability limits.
Disclosure of Invention
The present invention relates to a method and system for producing vinyl acetate.
According to one aspect of the invention, a method comprises: reacting a feed stream comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor to produce a crude vinyl acetate stream comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; the following conditions were measured and/or determined: the pressure of the feed stream or reactor, the temperature of the feed stream or reactor, and the concentration of at least one component in the feed stream; measuring and/or determining the oxygen content ([ O) in a feed stream 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the And when AFL min ＞FL-[O 2 ]If true, a shutdown procedure or corrective step is initiated, in which the minimum value (AFL) near the flammability limit min ) And a Flammability Limit (FL) equation based on the condition, and wherein the FL equation includes at least one interaction term.
According to one aspect of the invention, a method comprises: reacting a feed stream comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor to produce a crude vinyl acetate stream comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the tail gas stream comprises ethylene, carbon dioxide, alkanes, and oxygen, wherein the flash gas stream comprises ethylene, carbon dioxide, alkanes, and oxygen, and wherein the vinyl acetate stream comprises vinyl acetate, water, and acetic acid; heating the tail gas stream in a heat exchanger; the following conditions were measured and/or determined: pressure of heated tail gas stream, temperature of heated tail gas stream, and heated tail gas streamThe concentration of at least one component; measuring and/or determining the oxygen content ([ O) in the heated tail gas stream 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the And when AFL min ＞FL-[O 2 ]If true, a shutdown procedure or corrective step is initiated, in which the minimum value (AFL) near the flammability limit min ) And a Flammability Limit (FL) equation based on the condition, and wherein the FL equation includes at least one interaction term.
According to one aspect of the invention, a method comprises: reacting a feed stream comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor to produce a crude vinyl acetate stream comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the tail gas stream comprises ethylene, carbon dioxide, alkanes, and oxygen, wherein the flash gas stream comprises ethylene, carbon dioxide, alkanes, and oxygen, and wherein the vinyl acetate stream comprises vinyl acetate, water, and acetic acid; removing at least a portion of the carbon dioxide from the flash gas stream to produce CO 2 Removing the overhead distillation stream; the following conditions were measured and/or determined: CO 2 Removing pressure from the overhead stream, CO 2 Removing the temperature of the overhead stream, and CO 2 Removing the concentration of at least one component in the overhead stream; measurement and/or determination of CO 2 Removing oxygen content ([ O) from the top distillation stream 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the And when AFL min ＞FL-[O 2 ]If true, a shutdown procedure or corrective step is initiated, in which the minimum value (AFL) near the flammability limit min ) And a Flammability Limit (FL) equation based on the condition, and wherein the FL equation includes at least one interaction term.
According to one aspect of the invention, a method comprises: reacting a feed stream comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor to produce a crude vinyl acetate stream comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; the crude vinyl acetate streamSeparating into a tail gas stream, a flash gas stream, and a vinyl acetate stream, wherein the tail gas stream comprises ethylene, carbon dioxide, alkanes, and oxygen, wherein the flash gas stream comprises ethylene, carbon dioxide, alkanes, and oxygen, and wherein the vinyl acetate stream comprises vinyl acetate, water, and acetic acid; heating the tail gas stream in a heat exchanger; removing at least a portion of the carbon dioxide from the flash gas stream to produce CO 2 Removing the overhead distillation stream; combining vaporized acetic acid with a heated tail gas stream and CO 2 Removing the overhead stream and mixing in an evaporator to produce an vaporized stream; adding oxygen to the vaporized stream to produce a feed stream; measuring and/or determining the conditions according to (a), (b) and/or (c): (a) The pressure of the feed stream or reactor, the temperature of the feed stream or reactor, and the concentration of at least one component in the feed stream; (b) The pressure of the heated tail gas stream, the temperature of the heated tail gas stream, and the concentration of at least one component in the heated tail gas stream; (c) CO 2 Removing pressure from the overhead stream, CO 2 Removing the temperature of the overhead stream, and CO 2 Removing the concentration of at least one component in the overhead stream; and wherein (a) at a first minimum value (AFL) approaching the flammability limit min ) And a first Flammability Limit (FL) equation based on (a) conditions, where (b) is at a second minimum AFL min And a second FL formula based on the condition of (b), wherein (c) is at a third minimum AFL min And a third FL formula, based on the condition of (c), wherein one or more of the first FL formula, the second FL formula, and the third FL formula include at least one interaction term; measuring and/or determining the oxygen content ([ O) in a fluid selected from 2 ]): feed stream, heated tail gas stream, CO 2 Removing the overhead distillation stream, and any combination thereof; and when AFL is used for one or more of (a), (b) or (c) min ＞FL-[O 2 ]If true, a shutdown procedure or corrective step is initiated.
According to one aspect of the invention, a method comprises: reacting a feed stream comprising acetic acid, ethylene, oxygen, carbon dioxide, alkane, and water in a reactorTo produce a crude vinyl acetate stream comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream in a heat exchanger; separating the crude vinyl acetate stream into a tail gas stream, a flash gas stream and a vinyl acetate stream; passing a portion of the flash vapor stream to an ethylene recovery process having a vent stream; the following conditions were measured: the pressure of the vent stream, the temperature of the vent stream, and the concentration of at least one component in the vent stream, wherein the condition is at a minimum value (AFL) near the flammability limit min ) And a Flammability Limit (FL) equation including at least one interaction term; measuring oxygen content ([ O) in the effluent stream 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the AFL when used in connection with vent streams returned to ethylene recovery processes min ＞FL-[O 2 ]If true, the operating conditions of the ethylene recovery process are changed to AFL min ≤FL-[O 2 ]。
Drawings
The following figures are included to illustrate certain aspects of the embodiments and should not be taken as exclusive embodiments. The disclosed subject matter is capable of considerable modification, alteration, combination, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure.
The figure shows a process flow diagram of one example vinyl acetate production process of the present invention.
Detailed Description
As previously mentioned, vinyl acetate reactors operate based on flammability limits, which achieve safety, but significantly reduce reaction efficiency and thus increase manufacturing costs. Furthermore, where manufacturers monitor flammability at additional locations along the vinyl acetate production process, conventional calculations of the same flammability limits and/or establishment of non-flammability ranges are often used, even if the conditions (e.g., temperature and pressure) and components in the corresponding composition are different at different locations along the production process. Therefore, there is a need for a vinyl acetate production process that uses a more accurate flammability limit relationship throughout the vinyl acetate production process that provides safe control and improved operating efficiency.
The present invention relates to a method and system for producing vinyl acetate using a Flammability Limit (FL) equation with improved efficiency at more than one location of the vinyl acetate production process. Among them, FL can be used for four parts of the vinyl acetate production process: a reactor, an inter-process heat exchanger, a carbon dioxide removal system, and an ethylene recovery system (described in further detail herein).
The FL described herein is a function of operating conditions and includes at least one interaction term that represents the interrelationship of two or more operating conditions (e.g., temperature, pressure, and component concentration) on the FL. FL is generally expressed in units of mole percent oxygen. However, one skilled in the art will recognize that other units are acceptable.
Four types of interaction terms are described herein: component-component interaction terms, temperature-component interaction terms, pressure-component interaction terms, and pressure-temperature interaction terms. Each FL formula described herein includes at least one of the interaction terms described. Further, for each interaction item included, each FL described herein may include one or more of the interaction items described. For example, the first FL may include one component-component interaction item, two temperature-component interaction items, no pressure-component interaction item, and one pressure-temperature interaction item. Further, the second FL may include three component-component interaction items, two temperature-component interaction items, two pressure-component interaction items, and no pressure-temperature interaction items. Preferably, at least one (more preferably at least three) component-component interaction terms are included in the FL formula.
Equation 1a is a general formula for calculating the flammability limits described herein.
FL＝α+βP a +γT b +∑δ i [C i ] c +∑ε j I j Equation 1
Wherein FL is the flammability limit; alpha, beta, gamma, delta i And epsilon j Is a factor that can be experimentally determined for a given range of compositions, pressures and temperatures; p is pressure; t is the temperature; [ c ] i ]Is the concentration of C component per number i considered in the composition; i j Is j number of interaction items under consideration I; and a, b and c are orders (typically 1 or 2).
The number i of C-components considered in the composition for equation 1 may be 0 to 10 or more, or 1 to 10, or 2 to 7. The number j of I components considered in the composition for equation 1 may be 1 to 20 or more, or 1 to 15, or 2 to 10, or 4 to 12.
The interaction terms may be two or more operating conditions that are multiple times relative to one another (e.g., i=p d *[C] e (d and e are orders, typically 1) is an exemplary pressure-component interaction term, i=t f *[C] g (f and g are orders, typically 1) is an exemplary temperature-component interaction term, I= [ C ] 1 ] h *[C 2 ] k (h and k are orders, typically 1) is an exemplary component-component interaction term, where the two components may be the same or different, and i=p l *T m (l and m are orders, typically 1) are pressure-temperature interaction terms. Although shown herein as conditions for interaction item multiplication, other mathematical relationships may be used. For example, if an inverse relationship between two components is determined, the interaction term may include the first condition divided by the second condition, rather than the multiplication shown in the previous example.
The FL formula may include concentration terms for one or more components in the composition under consideration. Not all components of the contemplated compositions need be included in the FL formulation.
The FL formula may include at least one interaction term. Preferably, the FL includes at least one of each of the four interaction terms. More preferably, the FL comprises (a) two or more component-component interaction items, (b) one or more temperature-component interaction items, (c) one or more pressure-component interaction items, (d) a pressure-temperature interaction item, or (e) any combination of two or more of (a) - (d).
For example, equations 2 to 5 are examples of FL formulas.
FL＝α+βp a +γT b +∑ 1≤i≤10 δ i [C i ] c +∑ 1≤j≤50 ε j I j Equation 2
A value (AFL) close to the flammability limit is defined as the flammability limit of the composition and the oxygen content ([ O ] of the composition 2 ]) The difference between them is shown in equation 6. AFL is typically expressed in terms of mole percent of oxygen in a specified gas. However, those skilled in the art will recognize that other units are also acceptable, and that FL, AFL and [ O ] are acceptable for equation 6 2 ]The units of (c) should be identical.
AFL＝FL-[O 2 ]Equation 6
At AFL of 0, the oxygen content is equal to the flammability limit.
Each FL has a corresponding minimum AFL. Minimum AFL (AFL) min ) Is a threshold that provides a value close to FL that can be safely operated, where safe operation is at AFL min ≤FL-[O 2 ]Determination of AFL min Is known in the art and may include such considerations as uncertainty in the FL equation, sensor measurement limits, and sensor measurement accuracy (or error). European patent application 0845453A2 describes a method of determining a value close to the flammability limit and is incorporated herein by reference.
Each location in the system where FL is monitored has a corresponding sum FL formula (abbreviated herein as "AFL min /FL combination "). AFL (alpha-fettering language) min the/FL combination is generally unique to different locations within the vinyl acetate production process because of different considerations at each location. However, in some cases, both locations have the same AFL min /FL。
The system and method of the present invention may have AFL for one or more of the four portions of the vinyl acetate production process min Combination of/FL: reactor inlet, heat exchanger between processes, carbon dioxide removal system and ethylene recovery system (described in further detail herein). Preferably, two or more of said portions of the vinyl acetate production process have respective AFLs min and/FL combination. More preferably, three or four of said portions of the vinyl acetate production process have respective AFLs min and/FL combination. Most preferably, all four of the portions of the vinyl acetate production process have respective AFLs min and/FL combination.
The figure shows a process flow diagram of an exemplary vinyl acetate production process 100 of the present invention. Additional components and changes may be introduced to the method 100 without changing the scope of the invention. Furthermore, as will be appreciated by those skilled in the art, the description of the method 100 and related systems uses fluids to describe fluids passing through different lines. For each stream, the associated system has a respective line (e.g., a tube or other passageway through which a respective fluid or other material may readily pass) and optionally a valve, pump, compressor, heat exchanger or other device to ensure proper operation of the system, whether or not explicitly described.
Furthermore, descriptors for individual streams do not limit the composition of the streams to consist of the descriptors. For example, the ethylene stream need not consist of ethylene alone. Instead, the ethylene stream may comprise ethylene and a diluent gas (e.g., an inert gas). Alternatively, the ethylene stream may consist of ethylene alone. Alternatively, the ethylene stream may comprise ethylene, another reactant and optionally an inert component.
In the illustrated process 100, an acetic acid stream 102 and an ethylene stream 104 are introduced into an evaporator 106. Optionally, ethane may also be added to the evaporator 106. Additionally, one or more recycle streams 130, 158 (each described further herein) can also be introduced into the evaporator 106. Optionally, one or more recycle streams 130, 158 may be combined with acetic acid stream 102 (not shown) prior to introduction into evaporator 106.
The temperature and pressure of the evaporator 106 can vary over a wide range. The evaporator 106 is preferably operated at a temperature of 100 ℃ to 250 ℃, or 100 ℃ to 200 ℃, or 120 ℃ to 150 ℃. The operating pressure of the evaporator 106 is preferably 0.1MPa to 2.03MPa, or 0.25MPa to 1.75MPa, or 0.5MPa to 1.5MPa. The evaporator 106 produces an evaporated feed stream 108. Vaporized feed stream 108 exits vaporizer 106 and is combined with oxygen stream 110 to produce a combined feed stream 112. The combined feed stream 112 is analyzed by a sensor 114 before being fed to a vinyl acetate reactor 116.
Sensor 114 includes a water sensor to determine the water concentration in combined feed stream 112. The sensors 114 may also optionally include temperature sensors, pressure sensors, flow rate sensors, constituent sensors (e.g., gas chromatographs, infrared spectrometers, and oxygen analyzers), and the like, as well as any combination thereof. Individual sensors may each be present singly or in multiple. Having multiple specific sensors provides redundancy that minimizes downtime to replace the sensor and mitigates safety issues arising from sensor failure or misalignment. Although the sensor 114 is shown generally upstream of the vinyl acetate reactor 116, the sensor may be located elsewhere where calculations may be made to evaluate the reactor inlet or first AFL min the/FL combination is used for conditions (e.g., temperature, pressure or component concentration) at other suitable locations therein.
As described herein, many locations within the method 100 contain compositions that have the potential to become flammable if conditions are not monitored and adjusted as desired. Portions of the method 100 and related systems should operate to mitigate the risk of fire and explosion. One such location is the combined feed stream 112 under reaction conditions. Thus, the composition of the combined feed stream 112, the temperature of the combined feed stream 112 and/or the vinyl acetate reactor 116, and the pressure of the combined feed stream 112 and/or the vinyl acetate reactor 116 may be adjusted to provide safe operation of the vinyl acetate reactor 116.
The operating conditions in the vinyl acetate reactor 116 may be adjusted based on the composition of the combined feed stream 112. Generally, suitable ranges for the operating conditions of the vinyl acetate reactor 116 are provided below.
Regarding typical operating conditions of the vinyl acetate reactor 116, when vinyl acetate is produced, the molar ratio of ethylene to oxygen in the vinyl acetate reactor 116 is preferably less than 20:1 (e.g., 1:1 to 20:1, or 1:1 to 10:1, or 1.5:1 to 5:1, or 2:1 to 4:1). Further, the molar ratio of acetic acid to oxygen in vinyl acetate reactor 116 is preferably less than 10:1 (e.g., 0.5:1 to 10:1,0.5:1 to 5:1, or 0.5:1 to 3:1). The molar ratio of ethylene to acetic acid in vinyl acetate reactor 116 is preferably less than 10:1 (e.g., 1:1 to 10:1, or 1:1 to 5:1, or 2:1 to 3:1). Thus, the combined feed stream 112 comprises ethylene, oxygen, and acetic acid in the stated molar ratios.
The vinyl acetate reactor 116 may be a shell-and-tube reactor capable of absorbing heat generated by an exothermic reaction through a heat exchange medium and controlling the temperature thereof to a temperature range of 100 to 250 ℃, or 110 to 200 ℃, or 120 to 180 ℃. The pressure in the vinyl acetate reactor 116 may be maintained at 0.5MPa to 2.5MPa, or 0.5MPa to 2MPa.
Further, the vinyl acetate reactor 116 may be a fixed bed reactor or a fluidized bed reactor, preferably a fixed bed reactor, comprising a catalyst suitable for the acetoxylation of ethylene. Suitable catalysts for the production of vinyl acetate are described, for example, in U.S. Pat. nos. 3,743,607;3,775,342;5,557,014;5,990,344;5,998,659;6,022,823;6,057,260; and 6,472,556, each of which is incorporated herein by reference. Suitable catalysts may comprise palladium, gold, vanadium, and mixtures thereof. Particularly preferred are the catalysts palladium acetate/potassium acetate/cadmium acetate and palladium acetate/barium acetolaurate/potassium acetate. Typically, the palladium content of the catalyst is from 0.5wt% to 5wt%, or from 0.5wt% to 3wt%, or from 0.6wt% to 2wt%. When gold or one of its compounds is used, its addition ratio is 0.01wt% to 4wt%, or 0.2wt% to 2wt%, or 0.3wt% to 1.5wt%. The catalyst also preferably comprises a refractory support, preferably a metal oxide such as silica, silica-alumina, titania or zirconia, more preferably silica.
The operating conditions under which the vinyl acetate reactor 116 is operated may be based on the first AFL min and/FL combination. The first FL may be based on the pressure in the combined feed stream 112 or the vinyl acetate reactor 116, the temperature in the combined feed stream 112 or the vinyl acetate reactor 116, and the concentration of the individual components of the combined feed stream 112. Because the process 100 uses one or more recycle streams 130, 156, 168 and may contain diluents, the components in the combined feed stream 112 are more than ethylene, acetic acid, and oxygen. Examples of components of the combined feed stream 112 include, but are not limited to, ethylene, acetic acid, methane, ethane, propane, water, nitrogen, argon, and carbon dioxide, wherein the concentrations of the components (alone and/or in an interaction term) may be used in the first FL formulation (e.g., according to one of equations 1-5).
The concentrations of the components of the different streams described herein may be measured directly or calculated based on the measurement of the different components. For example, the acetic acid content (for dimerization) in the stream may be calculated based on the measurements. The acetic acid content can then be deduced from the water content. Furthermore, the measurement or a value derived from the measurement need not be at the location of interest. For example, the water content at the reactor inlet may be deduced from the water content of the recycle stream from the purification process 148 (mentioned in paragraph 55, but not shown in the figure). Thus, when a condition value (e.g., a temperature value, a pressure value, or a stream component concentration) is described herein, the condition value is not limited to being measured directly at the location, but includes a value of the location that is deduced based on measurements at that or other locations in the method 100.
Discussion of FL equation derivation is provided in the examples section. The first FL may be based on the pressure of the vinyl acetate reactor 116, acetic acidThe temperature of the vinyl ester reactor 116 and the concentration of the individual components at the inlet of the vinyl acetate reactor 116. Further, in general, the first FL formula may include at least one interaction term. Preferably, the first FL formula includes at least one of each of the four interaction terms. More preferably, the first FL formulation comprises (a) two or more component-component interaction items, (b) one or more temperature-component interaction items, (c) one or more pressure-component interaction items, (d) a pressure-temperature interaction item, or (e) any combination of two or more of (a) to (d). Components that may be included in the interaction term of the first FL formula include, but are not limited to, ethane concentration ([ C) 2 H 6 ]) Methane concentration ([ CH ] 4 ]) Carbon dioxide concentration ([ CO ] 2 ]) Acetic acid concentration ([ HAc)]) Concentration of water ([ H) 2 O]) Ethylene concentration ([ C) 2 H 4 ]) Propane concentration ([ C) 3 H 8 ]) And any combination thereof. Thus, examples of interaction terms that may be included in the first FL formula may include, but are not limited to, P T, P C 2 H 6 ]，P*[CH4]，P*[CO 2 ]，P*[HAc]，P*[H 2 O]，P*[C 2 H 4 ]，P*[C 3 H 8 ]，T*[C 2 H 6 ]，T*[CH 4 ]，T*[CO 2 ]，T*[HAc]，T*[H 2 O]，T*[C 2 H 4 ]，T*[C 3 H 8 ]，[C 2 H 6 ]*[CH 4 ]，[C 2 H 6 ]*[CO 2 ]，[C 2 H 6 ]*[HAc]，[C 2 H 6 ]*[H 2 O]，[C 2 H 6 ]*[C 2 H 4 ]，[C 2 H 6 ]*[C 3 H 8 ]，[CH 4 ]*[CO 2 ]，[CH 4 ]*[HAc]，[CH 4 ]*[H 2 O]，[CH 4 ]*[C 2 H 4 ]，[CH 4 ]*[C 3 H 8 ]，[CO 2 ]*[HAc]，[CO 2 ]*[H 2 O]，[CO 2 ]*[C 2 H 4 ]，[CO 2 ]*[C 3 H 8 ]，[HAc]*[H 2 O]，[HAc]*[C 2 H 4 ]，[HAc]*[C 3 H 8 ]，[H 2 O]*[C 2 H 4 ]，[H 2 O]*[C 3 H 8 ]，[C 2 H 4 ]*[C 3 H 8 ]And any combination thereof. If an inert gas is used to change the heat capacity of the gas mixture, an inert gas may optionally be included. Thus, examples of interaction terms that may be further included in the first FL formula may include, but are not limited to, P ]T & lt inert & gt](inert)]＊[C 2 H 6 ](inert)]＊[CH 4 ](inert)]＊[CO 2 ](inert)]＊[HAc](inert)]＊[H 2 O](inert)]＊[C 2 H 4 ](inert)]＊[C 3 H 8 ][ inert a ]]Inert b]And any combination thereof. Examples of inert gases used in the production of vinyl acetate include, but are not limited to, argon, nitrogen, and the like, and any combination thereof. In the previous example (two lists) of an interaction item, the corresponding above-mentioned order for each component of the interaction item is 1. However, other orders (e.g., -2, -1, -0.5,0.5,1,2, etc.) may be used.
The conditions of the vinyl acetate reactor 116 may be monitored and used to calculate the first FL and confirm violation of the first minimum AFL. For example, while operating, the first FL is continuously calculated to show changes in operating conditions (e.g., pressure, temperature, and concentration of individual components of the combined feed stream 112), and the oxygen content (mole percent of oxygen) in the combined feed stream 112 is continuously measured to ensure that the minimum AFL (i.e., AFL) min ≤FL-[O 2 ]) And (5) internal operation. If the minimum AFL is violated (i.e., real-time AFL is less than the minimum AFL or AFL min ＞FL-[O 2 ]) The method 100 may enter a shutdown procedure or undergo a corrective step so as not to violate the minimum AFL.
Referring again to the drawing, the vinyl acetate in reactor 116 reacts to produce a crude vinyl acetate stream 118. Depending on the conversion and reaction conditions, the crude vinyl acetate stream 118 may comprise 5wt% to 30wt% vinyl acetate, 5wt% to 40wt% acetic acid, 0.1wt% to 10wt% water, 10wt% to 80wt% ethylene, 1wt% to 40wt% carbon dioxide, 0.1wt% to 50wt% alkanes (e.g., methane, ethane, or mixtures thereof), and 0.1wt% to 15wt% oxygen. Optionally, the crude vinyl acetate stream 118 may also comprise 0.01wt% to 10wt% ethyl acetate. The crude vinyl acetate stream 118 may contain other compounds such as methyl acetate, acetaldehyde, acrolein, propane, and inerts such as nitrogen or argon. Typically, these other compounds are present in very low amounts, in addition to the inerts.
The crude vinyl acetate stream 118 is passed through a heat exchanger 120 to reduce the temperature of the crude vinyl acetate stream 118 and then to a separator 122 (e.g., a distillation column). Preferably, the crude vinyl acetate stream 118 is cooled to a temperature of 80 ℃ to 145 ℃, or 90 ℃ to 135 ℃ prior to introduction into the separator 122. Preferably, condensation of the liquefiable components does not occur and the cooled crude vinyl acetate stream 118 is introduced as a gas into the separator 122.
Energy for separating components of the crude vinyl acetate stream 118 may be provided by the heat of reaction in the reactor 116. In some embodiments, a reboiler may optionally be present, dedicated to increasing the separation energy within separator 122.
Separator 122 separates the crude vinyl acetate stream 118 into at least two streams: a top distillation stream 124 and a bottom stream 126. Top distillation stream 124 can comprise ethylene, carbon dioxide, water, alkanes (e.g., methane, ethane, propane, or mixtures thereof), oxygen, and vinyl acetate. The bottom stream may comprise vinyl acetate, acetic acid, water and possibly ethylene, carbon dioxide and alkanes.
Top distillation stream 124 is sent to a scrubber 128 to remove vinyl acetate from top distillation stream 124. As a result, scrubber 128 has a tail gas stream 130 and a bottom stream 132. The vinyl acetate wash may be achieved by passing the top distillate stream 124 through a mixture of water and acetic acid.
The tail gas stream 130 comprises ethylene, carbon dioxide, alkanes, and oxygen. Conditions (e.g., temperature, pressure, and/or composition of the constituents) of the exhaust stream 130 may be measured using the sensor 134. The sensor 134 may include, but is not limited to, a temperature sensor, a pressure sensor, a flow rate sensor, constituent sensors (e.g., gas chromatograph, infrared spectrometer, and oxygen analyzer), and the like, as well as any combination thereof. Individual sensors may each be present singly or in multiple. Having multiple specific sensors provides redundancy that minimizes downtime to replace the sensor and mitigates safety issues arising from sensor failure or misalignment. While the sensor 134 is generally shown downstream of the scrubber 128 along the exhaust stream 130, the sensor may be located at other locations where calculations may be made to evaluate the condition (e.g., temperature, pressure, or component concentration) of the exhaust stream 130 after the scrubber 128.
The tail gas stream 130 (also referred to as a recycle stream) is sent back to the evaporator 106 through the heat exchanger 120 where the crude vinyl acetate stream 118 heats the tail gas stream 130. Optionally, the tail gas stream 130 can be augmented with or otherwise added to other streams, including other recycle streams (not shown) and feed streams in the process. As shown, an ethylene feed stream 136 and a methane feed stream 138 (or other steady (ballast) gas stream) are combined with (e.g., mixed with or entrained with) the tail gas stream 130.
Further, other processes (not shown) may be performed on the tail gas stream 130 between the scrubber 128 and the heat exchanger 120. For example, the tail gas stream 130 can have at least a portion of the carbon dioxide removed.
The tail gas stream 130 is potentially flammable and/or explosive after being heated in the heat exchanger 120. Therefore, the second AFL min the/FL combination can be used in the method and system of the present invention to monitor the flammability of the tail gas stream 130 prior to introduction into the evaporator.
Thus, between the heat exchanger 120 and the evaporator 106, the exhaust gas stream 130 is analyzed by the sensor 140. Examples of sensors 140 include, but are not limited to, temperature sensors, pressure sensors, flow rate sensors, constituent sensors (e.g., gas chromatograph, infrared spectrometer, and oxygen analyzer), and the like, as well as any combination thereof. Individual sensors may each be present singly or in multiple. Having multiple specific sensors provides redundancy that minimizes downtime for replacement of the sensors andand the safety problem caused by sensor failure or miscorrection is relieved. While the sensor 140 is shown generally between the heat exchanger 120 and the evaporator 106, the sensor may be located elsewhere where calculations may be made to evaluate conditions (e.g., temperature, pressure, or component concentration) between the heat exchanger 120 and the evaporator 106, or at a second AFL min Other suitable locations for the/FL combination application.
Discussion of FL equation derivation is provided in the examples section. The second FL may be based on the pressure in the line containing the exhaust stream 130, the temperature of the exhaust stream 130, and the concentration of the individual components of the exhaust stream 130. Also, in general, the second FL formula can include at least one interaction term. Preferably, the second FL formula includes at least one of each of the four interaction terms. More preferably, the second FL formulation comprises (a) two or more component-component interaction items, (b) one or more temperature-component interaction items, (c) one or more pressure-component interaction items, (d) a pressure-temperature interaction item, or (e) any combination of two or more of (a) to (d). Examples of components in the vinyl acetate reactor 116, where the concentration of the components may be used in the second FL formula (e.g., according to one of equations 1-5), include, but are not limited to, ethylene, methane, ethane, propane, and carbon dioxide. Components that may be included in the interaction term of the second FL formula include, but are not limited to, ethane concentration ([ C) 2 H 6 ]) Methane concentration ([ CH ] 4 ]) Carbon dioxide concentration ([ CO ] 2 ]) Ethylene concentration ([ C) 2 H 4 ]) Propane concentration ([ C) 3 H 8 ]) And any combination thereof. Thus, examples of interaction terms that may be included in the second FL formula may include, but are not limited to, P T, P C 2 H 6 ]，P*[CH 4 ]，P*[CO 2 ]，P*[C 2 H 4 ]，P*[C 3 H 8 ]，T*[C 2 H 6 ]，T*[CH 4 ]，T*[CO 2 ]，T*[C 2 H 4 ]，T*[C 3 H 8 ]，[C 2 H 6 ]*[CH 4 ]，[C 2 H 6 ]*[CO 2 ]，[C 2 H 6 ]*[C 2 H 4 ]，[C 2 H 6 ]*[C 3 H 8 ]，[CH 4 ]*[CO 2 ]，[CH 4 ]*[C 2 H 4 ]，[CH 4 ]*[C 3 H 8 ]，[CO 2 ]*[C 2 H 4 ]，[CO 2 ]*[C 3 H 8 ]，[C 2 H 4 ]*[C 3 H 8 ]And any combination thereof. If an inert gas is used to change the heat capacity of the gas mixture, an inert gas may optionally be included. Thus, examples of interaction terms that may be further included in the second FL formula may include, but are not limited to, P [ inert ]]T is [ inert ]](inert)]*[C 2 H 6 ](inert)]*[CH 4 ](inert)]*[CO 2 ](inert)]*[HAc](inert)]*[H 2 O](inert)]*[C 2 H 4 ](inert)]*[C 3 H 8 ][ inert a ]]* [ inert b ]]And any combination thereof. Examples of inert gases used in the production of vinyl acetate include, but are not limited to, argon, nitrogen, and the like, and any combination thereof. In the previous example (two lists) of an interaction item, the corresponding above-mentioned order for each component of the interaction item is 1. However, other orders (e.g., -2, -1, -0.5,0.5,1,2, etc.) may be used.
Conditions of the exhaust stream 130 may be monitored and used to calculate the second FL and determine violations for the second minimum AFL. For example, while operating, a second FL is continuously calculated to show changes in operating conditions (e.g., pressure, temperature, and concentration of individual components of the exhaust stream 130), and the oxygen content (mole percent of oxygen) in the exhaust stream 130 is continuously measured to ensure that the fuel is at a second minimum AFL (i.e., AFL min ≤FL-[O 2 ]) And (5) internal operation. If the second minimum AFL is violated (i.e. real-time AFL is less than the minimum AFL or AFL min ＞FL-[O 2 ]) The method 100 may enter a shutdown procedure or undergo a corrective step so as not to violate the minimum AFL.
Referring again to the figures, the bottom stream 126 from the separator 122 and the bottom stream 132 from the scrubber 128 may be combined and fed to a coarse tank 142. Typically, the fluid entering the rough tank 142 is depressurized to a pressure of 0.1MPa to 0.15 MPa. In reduced pressure, the incoming stream, ethylene, carbon dioxide, inert gases (e.g., nitrogen and/or argon) and acetic acid are flashed to produce flash stream 144. The bottom of the crude tank 142 contains primarily vinyl acetate, water and acetic acid, and some ethyl acetate by-product. The bottoms are sent as a vinyl acetate stream 146 to be purified by various methods 148 to produce a purified vinyl acetate product stream 150. Examples of purification methods 148 include, but are not limited to, azeotropic distillation, water stripping, distillation, phase separation, and the like, and any combination thereof. Examples of different processing methods and systems are described in U.S. patent 6,410,817,8,993,796 and 9,045,413 and U.S. patent application publication 2014/0066649, each of which is incorporated herein by reference.
Further, the purification process 148 can produce additional streams, either singly or in any combination, that can be recycled back to the evaporator 106, the tail gas stream 130, the flash gas stream 144, and/or other streams within the process 100.
Optionally (not shown), a portion of the tail gas slipstream 130 can be combined with (e.g., mixed with or entrained with) the flash gas stream 144.
At least a portion of the carbon dioxide in flash stream 144 (optionally already combined with a portion of tail gas slip stream 130) is removed prior to being recycled back to evaporator 106. As shown, flash gas stream 144 first passes through CO 2 Scrubber 152 then passes through CO 2 Absorber 156 to produce CO 2 Top distillate stream 158 is removed. In CO 2 Scrubber 152 and CO 2 Between the absorbers 156, ethylene can be added to the flash gas stream 144 from the ethylene stream 154.
CO 2 Removal of top distillation stream 158 is another potentially flammable or explosive composition in which the oxygen content of the methods and systems described herein may be monitored. Therefore, the third AFL min the/FL combination may be used in the method and system of the present invention to monitor CO 2 The flammability of the top distillate stream 158 is removed.
Thus, in CO 2 After absorber 156, CO is analyzed with sensor 160 2 Removal ofTop distillation stream 158. Examples of sensors 160 include, but are not limited to, temperature sensors, pressure sensors, flow rate sensors, constituent sensors (e.g., gas chromatograph, infrared spectrometer, and oxygen analyzer), and the like, as well as any combination thereof. Individual sensors may each be present singly or in multiple. Having multiple specific sensors provides redundancy that minimizes downtime to replace the sensor and mitigates safety issues arising from sensor failure or misalignment. Although sensor 160 is shown generally at CO 2 Downstream of absorber 156, but the sensor 160 may be located elsewhere where calculations may be made to evaluate the CO 2 Conditions downstream of absorber 156 (e.g., temperature, pressure, or component concentration), or placed in a third AFL min Other suitable locations for use therein are the/FL combinations.
Discussion of the derivation of the FL equation is provided in the examples section. The third FL may be based on the content of CO 2 The pressure in the line of overhead stream 158, CO, is removed 2 Removal of temperature and CO from overhead stream 158 2 The concentration of the individual components of the top distillation stream 158 is removed. Also, in general, the third FL formula can include at least one interaction term. Preferably, the third FL formula includes at least one of each of the four interaction terms. More preferably, the third FL formulation comprises (a) two or more component-component interaction items, (b) one or more temperature-component interaction items, (c) one or more pressure-component interaction items, (d) a pressure-temperature interaction item, or (e) any combination of two or more of (a) to (d). Examples of components in the vinyl acetate reactor 116, where the concentration of the components may be used in the third FL formula (e.g., according to one of equations 1-5), include, but are not limited to, ethylene, methane, ethane, propane, and carbon dioxide. Components that may be included in the interaction term of the second FL formula include, but are not limited to, ethane concentration ([ C) 2 H 6 ]) Methane concentration ([ CH ] 4 ]) Carbon dioxide concentration ([ CO ] 2 ]) Ethylene concentration ([ C) 2 H 4 ]) Propane concentration ([ C) 3 H 8 ]) And any combination thereof. Thus, the phase that may be included in the third FL formulaExamples of interaction items may include, but are not limited to, P T, P C 2 H 6 ]，P*[CH 4 ]，P*[CO 2 ]，P*[C 2 H 4 ]，P*[C 3 H 8 ]，T*[C 2 H 6 ]，T*[CH 4 ]，T*[CO 2 ]，T*[C 2 H 4 ]，T*[C 3 H 8 ]，[C 2 H 6 ]*[CH 4 ]，[C 2 H 6 ]*[CO 2 ]，[C 2 H 6 ]*[C 2 H 4 ]，[C 2 H 6 ]*[C 3 H 8 ]，[CH 4 ]*[CO 2 ]，[CH 4 ]*[C 2 H 4 ]，[CH 4 ]*[C 3 H 8 ]，[CO 2 ]*[C 2 H 4 ]，[CO 2 ]*[C 3 H 8 ]，[C 2 H 4 ]*[C 3 H 8 ]And any combination thereof. If an inert gas is used to change the heat capacity of the gas mixture, an inert gas may optionally be included. Thus, examples of interaction terms that may be further included in the second FL formula may include, but are not limited to, P]T & lt inert & gt](inert)]＊[C 2 H 6 ](inert)]＊[CH 4 ](inert)]＊[CO 2 ](inert)]＊[HAc](inert)]＊[H 2 O](inert)]＊[C 2 H 4 ](inert)]＊[C 3 H 8 ][ inert a ]]Inert b]And any combination thereof. Examples of inert gases used in the production of vinyl acetate include, but are not limited to, argon, nitrogen, and the like, and any combination thereof. In the previous example (two lists) of an interaction item, the corresponding above-mentioned order for each component of the interaction item is 1. However, other orders (e.g., -2, -1, -0.5,0.5,1,2, etc.) may be used.
Because of the tail gas stream 130 and CO 2 The removed overhead stream 158 has a similar composition, so the second FL equation and the third FL equation may be the same. However, the second minimum AFL and the third minimum AFL may be different, as different sensors may be used.
CO 2 Conditions for removal of overhead stream 158May be monitored and used to calculate the third FL and to determine violations of the third minimum AFL. For example, while operating, a third FL is continuously calculated to display operating conditions (e.g., pressure, temperature, and CO 2 Concentration of individual components removed from top distillation stream 158) and continuously measuring CO 2 The oxygen content (mole percent oxygen) in top distillation stream 158 is removed to ensure that the concentration of oxygen in the top distillation stream is at a third minimum AFL (i.e., AFL min ≤FL-[O 2 ]) And (5) internal operation. If the third minimum AFL is violated (i.e. real-time AFL is less than the minimum AFL or AFL min ＞FL-[O 2 ]) The method 100 may enter a shutdown procedure or undergo a corrective step so as not to violate the minimum AFL.
Referring again to the drawings, CO 2 The top distillate stream 158 is removed and can then pass through a heat exchanger 162 and feed into the evaporator 106. In addition, use is made of the flash gas stream 144 and/or CO 2 A slip stream 164 of top distillation stream 158 is removed to purge inerts from the system. The slip stream 164 may be sent to an ethylene recovery process 166. The ethylene recovery process 162 produces an ethylene vent stream 168 and a recycle stream 172.
Examples of ethylene recovery processes 166 may include, but are not limited to, a washing system, a membrane recovery process, and the like, as well as any combination thereof.
The ethylene recovery process 166 can produce a vent stream 168 and an additional stream 172 that carry recovered ethylene to other processes or recycle back to the process 100.
The vent stream 168 of the ethylene recovery process 166 and the associated output stream are additional potentially flammable or explosive compositions in which the oxygen content of the methods and systems described herein can be monitored. Therefore, the fourth AFL min the/FL combination may be used in the method and system of the present invention to monitor the flammability of the ethylene vent stream 168.
Thus, after the ethylene recovery process 166, the ethylene vent stream 168 is analyzed with a sensor 170. Examples of the sensor 170 include, but are not limited to, a temperature sensor, a pressure sensor, a flow rate sensor, constituent sensors (e.g., gas chromatograph, infrared spectrometer, and oxygen analyzer), and the like, as well as any combination thereof. Single passThe sensors may each be present singly or in multiple. Having multiple specific sensors provides redundancy that minimizes downtime to replace the sensor and mitigates safety issues arising from sensor failure or misalignment. Although the sensor 170 is shown generally along the ethylene vent stream 168, the sensor 170 may be located elsewhere where calculations may be made to evaluate the condition (e.g., temperature, pressure, or component concentration) of the ethylene vent stream 168, or at a fourth AFL min Other suitable locations for use therein are the/FL combinations.
Discussion of the derivation of the FL equation is provided in the examples section. The fourth FL may be based on the pressure in the line containing the ethylene vent stream 168, the temperature of the ethylene vent stream 168 and the concentration of the individual components of the ethylene vent stream 168. Also, in general, the fourth FL formula can include at least one interaction term. Preferably, the fourth FL formula includes at least one of each of the four interaction terms. More preferably, the fourth FL formulation comprises (a) two or more component-component interaction items, (b) one or more temperature-component interaction items, (c) one or more pressure-component interaction items, (d) a pressure-temperature interaction item, or (e) any combination of two or more of (a) to (d). Examples of components in the vinyl acetate reactor 116, where the concentration of the components may be used in the fourth FL equation (e.g., according to one of equations 1-5), include, but are not limited to, ethylene, methane, ethane, propane, and carbon dioxide. Components that may be included in the interaction term of the second FL formula include, but are not limited to, ethane concentration ([ C) 2 H 6 ]) Methane concentration ([ CH ] 4 ]) Carbon dioxide concentration ([ CO ] 2 ]) Ethylene concentration ([ C) 2 H 4 ]) Propane concentration ([ C) 3 H 8 ]) And any combination thereof. Thus, examples of interaction terms that may be included in the second FL formula may include, but are not limited to, P T, P C 2 H 6 ]，P*[CH 4 ]，P*[CO 2 ]，P*[C 2 H 4 ]，P*[C 3 H 8 ]，T*[C 2 H 6 ]，T*[CH 4 ]，T*[CO 2 ]，T*[C 2 H 4 ]，T*[C 3 H 8 ]，[C 2 H 6 ]*[CH 4 ]，[C 2 H 6 ]*[CO 2 ]，[C 2 H 6 ]*[C 2 H 4 ]，[C 2 H 6 ]*[C 3 H 8 ]，[CH 4 ]*[CO 2 ]，[CH 4 ]*[C 2 H 4 ]，[CH 4 ]*[C 3 H 8 ]，[CO 2 ]*[C 2 H 4 ]，[CO 2 ]*[C 3 H 8 ]，[C 2 H 4 ]*[C 3 H 8 ]And any combination thereof. If an inert gas is used to change the heat capacity of the gas mixture, an inert gas may optionally be included. Thus, examples of interaction terms that may be further included in the second FL formula may include, but are not limited to, P]T & lt inert & gt](inert)]＊[C 2 H 6 ](inert)]＊[CH 4 ](inert)]＊[CO 2 ](inert)]＊[HAc](inert)]＊[H 2 O](inert)]＊[C 2 H 4 ](inert)]＊[C 3 H 8 ][ inert a ]]Inert b]And any combination thereof. Examples of inert gases used in the production of vinyl acetate include, but are not limited to, argon, nitrogen, and the like, and any combination thereof. In the previous example (two lists) of an interaction item, the corresponding above-mentioned order for each component of the interaction item is 1. However, other orders (e.g., -2, -1, -0.5,0.5,1,2, etc.) may be used.
Conditions of the ethylene recovery process 166 and/or the ethylene vent stream 168 may be monitored and used to calculate the fourth FL and determine violation of the fourth minimum AFL. For example, while operating, a fourth FL is continuously calculated to show changes in operating conditions (e.g., pressure, temperature, and concentration of individual components of the ethylene vent stream 164), and the oxygen content (mole percent of oxygen) in the ethylene vent stream 164 is continuously measured to ensure that the fuel is at a fourth minimum AFL (i.e., AFL) min ≤FL-[O 2 ]) And (5) internal operation. Because of some independence of the ethylene recovery process 166 and/or the ethylene vent stream 168 from the remainder of the process 100, violation of the fourth minimum AFL (i.e., real-time AFL is less than the minimum value)AFL or AFL min ＞FL-[O 2 ]) Resulting in less vigorous action than the shut down method 100. Typically, the operating conditions of the ethylene recovery process 166 are changed to return the ethylene recovery process 166 and/or the ethylene vent stream 168 to safe operation. For example, the slipstream 164 flow rate may be varied and/or a diluent gas (e.g., an inert gas such as nitrogen or argon) may be added to stream 168. Other suitable actions will be apparent to those skilled in the art that may be employed to return the ethylene recovery process 166 and/or the ethylene vent stream 168 to safe operation.
Although the figures generally show process 100, one of ordinary skill in the art will know how to apply the teachings of the present invention to other vinyl acetate production processes, which may vary from the process 100 shown. Examples of different vinyl acetate production processes and systems are described in U.S. patent 6,410,817,8,993,796 and 9,045,413 and U.S. patent application publication 2014/0066649, each of which is incorporated herein by reference.
Detailed Description
The first non-limiting embodiment method of the present invention comprises: reacting a feed stream 112 comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; the following conditions were measured and/or determined: the pressure of the feed stream 112 or the reactor 116, the temperature of the feed stream 112 or the reactor 116, and the concentration of at least one component in the feed stream 112; oxygen content ([ O) of feed stream 112 is measured and/or determined 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the And when AFL min ＞FL-[O 2 ]If true, a shutdown procedure or corrective step is initiated, in which the minimum value (AFL) near the flammability limit min ) And a Flammability Limit (FL) equation based on the condition, and wherein the FL equation includes at least one interaction term.
A second non-limiting embodiment of the present invention method comprises: a feed stream 112 comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water is reacted in a reactor 116 to produce a catalyst comprising vinyl acetate, acetic acidA crude vinyl acetate stream 118 of water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, wherein the tail gas stream 130 comprises ethylene, carbon dioxide, alkanes, and oxygen, wherein the flash gas stream 144 comprises ethylene, carbon dioxide, alkanes, and oxygen, and wherein the vinyl acetate stream 146 comprises vinyl acetate, water, and acetic acid; heating the tail gas stream 130 in heat exchanger 120; the following conditions were measured and/or determined: the pressure of the heated tail gas stream 130, the temperature of the heated tail gas stream 130, and the concentration of at least one component of the heated tail gas stream 130; oxygen content ([ O) of the heated tail gas stream 130 is measured and/or determined 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the And when AFL min ＞FL-[O 2 ]If true, a shutdown procedure or corrective step is initiated, in which the minimum value (AFL) near the flammability limit min ) And a Flammability Limit (FL) equation based on the condition, and wherein the FL equation includes at least one interaction term.
A third non-limiting embodiment of the present invention method comprises: reacting a feed stream 112 comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, wherein the tail gas stream 130 comprises ethylene, carbon dioxide, alkanes, and oxygen, wherein the flash gas stream 144 comprises ethylene, carbon dioxide, alkanes, and oxygen, and wherein the vinyl acetate stream 146 comprises vinyl acetate, water, and acetic acid; removing at least a portion of the carbon dioxide from the flash gas stream 144 to produce CO 2 Removing overhead distillation stream 158; the following conditions were measured and/or determined: CO 2 Removal of pressure of overhead stream 158, CO 2 Removing the temperature of top distillation stream 158, and CO 2 Removing the concentration of at least one component in top distillation stream 158; measurement and/or determination of CO 2 Removal ofOxygen content ([ O) of top distillate stream 158 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the And when AFL min ＞FL-[O 2 ]If true, a shutdown procedure or corrective step is initiated, in which the minimum value (AFL) near the flammability limit min ) And a Flammability Limit (FL) equation based on the condition, and wherein the FL equation includes at least one interaction term.
Two or more of the first, second and third embodiment methods may be performed together. For example, the first and second embodiment methods may be performed together. In another embodiment, the first and third embodiment methods may be performed together. In yet another embodiment, the second and third embodiment methods may be performed together. In another embodiment, the first, second and third embodiment methods may be performed together. In addition, recirculation of fluids and other method steps described herein may be performed in combination with one or more of the first, second, and third embodiment methods.
A fourth non-limiting embodiment of the present invention method comprises: reacting a feed stream 112 comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, wherein the tail gas stream 130 comprises ethylene, carbon dioxide, alkanes, and oxygen, wherein the flash gas stream 144 comprises ethylene, carbon dioxide, alkanes, and oxygen, and wherein the vinyl acetate stream 146 comprises vinyl acetate, water, and acetic acid; heating the tail gas stream 130 in heat exchanger 120; removing at least a portion of the carbon dioxide from the flash gas stream 144 to produce CO 2 Removing overhead distillation stream 158; vaporized acetic acid and heated tail gas stream 130 and CO 2 The removed overhead stream 158 is combined in the evaporator 106 to produce an vaporized stream 108; oxygen is added to the vaporized stream 108 to produce a feed stream 112; measuring and/or determining the conditions according to (a), (b) and/or (c): (a) Pressure of feed stream 112 or reactor 116, temperature of feed stream 112 or reactor 116And the concentration of at least one component in the feed stream 112; (b) The pressure of the heated tail gas stream 130, the temperature of the heated tail gas stream 130, and the concentration of at least one component of the heated tail gas stream 130; (c) CO 2 Removal of pressure of overhead stream 158, CO 2 Removing the temperature of top distillation stream 158, and CO 2 Removing the concentration of at least one component in top distillation stream 158; and wherein (a) at a first minimum value (AFL) approaching the flammability limit min ) And a first Flammability Limit (FL) equation based on (a) conditions, where (b) is at a second minimum AFL min And a second FL formula based on the condition of (b), wherein (c) is at a third minimum AFL min And a third FL formula, based on the condition of (c), wherein one or more of the first FL formula, the second FL formula, and the third FL formula include at least one interaction term; measuring and/or determining the oxygen content ([ O) of a fluid selected from 2 ]): feed stream 112, heated tail gas stream 130, CO 2 Removing overhead distillation stream 158 and any combination thereof; and when AFL is used for one or more of (a), (b) or (c) min ＞FL-[O 2 ]If true, a shutdown procedure or corrective step is initiated. The fourth non-limiting example method may further comprise one or more of the following: element 1: wherein the first FL equation, the second FL equation, and/or the third FL equation are according to equation 1; element 2: wherein the first AFL min Different from the second AFL min And/or a first AFL min Different from the third AFL min And/or a second AFL min Different from the third AFL min The method comprises the steps of carrying out a first treatment on the surface of the Element 3: wherein the first FL formula is different from the second FL formula and/or the first FL formula is different from the third FL formula and/or the second FL formula is different from the third FL formula; element 4: wherein the at least one interaction item is selected from: a component-component interaction item, a temperature-component interaction item, a pressure-temperature interaction item, and any combination thereof; element 5: wherein the second first equation, the second FL equation, and/or the third FL equation include one or more terms selected from the group consisting of: constant, temperature, pressure, concentration of components in the corresponding composition A degree; element 6: wherein the first FL formula and/or the second FL formula and/or the third FL formula include at least two component-component interaction terms; element 7: wherein the first FL formula and/or the second FL formula and/or the third FL formula comprises at least one pressure-component item, at least one temperature-component interaction item, a pressure-temperature interaction item, and at least two component-component interaction items; element 8: wherein at least one interaction item is 3 to 15 interaction items; element 9: the method further comprises the steps of: combining a portion of tail gas slipstream 130 with flash gas stream 144 prior to removing at least a portion of the carbon dioxide from flash gas stream 144; element 10: wherein separating the crude vinyl acetate stream 118 comprises: the crude vinyl acetate stream 118 is separated in separator 122 into a top distillate stream 124 and a first bottom stream 126; overhead stream 124 is separated in scrubber 128 into a tail gas stream 130 and a second bottom stream 132; first and second bottom streams 126, 132 are combined; and separating the combined first and second bottoms streams 126, 132 in a crude drum 142 into a flash gas stream 144 and a vinyl acetate stream 146; element 11: the method further comprises the steps of: purifying the vinyl acetate stream 146 into a purified vinyl acetate product stream 150; element 12: the method further comprises the steps of: purifying the vinyl acetate stream 146 into a purified vinyl acetate product stream 150 and one or more additional streams; and recycling at least one of the additional streams back to the evaporator 106, the tail gas stream 130 or the flash gas stream 144; element 13: the method further comprises the steps of: adding ethylene and/or methane to the tail gas stream 130 upstream of the heat exchanger 120; element 14: the method further comprises the steps of: removing at least a portion of the carbon dioxide from the tail gas stream 130 upstream of the heat exchanger 120; element 15: the method further comprises the steps of: ethylene and/or acetic acid is added to the evaporator 106; element 16: the method further comprises the steps of: a portion of the flash gas stream 144 is passed to an ethylene recovery process 166 having a vent stream 168; the following conditions were measured: the pressure of the exhaust stream 168, the temperature of the exhaust stream 168, and the concentration of at least one component in the exhaust stream 168, wherein the condition is at a fourth minimum value (AFL) near the flammability limit min ) And a fourth Flammability Limit (FL) equation including at least one interaction term; oxygen content ([ O) of the effluent stream 168 is measured 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the And when AFL is used for vent stream 168 returned to ethylene recovery process 166 min ＞FL-[O 2 ]When true, the operating conditions of the ethylene recovery process 166 are changed to AFL min ≤FL-[O 2 ]. Element 17: element 16 and wherein fourth AFL min Different from the first AFL min And/or a second AFL min And/or a third AFL min The method comprises the steps of carrying out a first treatment on the surface of the Element 18: element 16 and wherein the fourth FL formula is different from the first FL formula and/or the second FL formula and/or the third FL formula; element 19: element 16 and wherein the at least one interaction term for the fourth FL formula is selected from: component-component interaction items, temperature-component interaction items, pressure-temperature interaction items, and any combination thereof; element 20: element 16 and wherein the second first equation, the second FL equation, and/or the third FL equation include one or more items selected from the group consisting of: constant, temperature, pressure, component concentrations of the corresponding composition; element 21: element 16 and wherein the fourth FL formulation includes at least two component-component interaction terms; element 22: element 16 and wherein the fourth FL formula includes at least one pressure-component item, at least one temperature-component interaction item, one pressure-temperature interaction item and at least two component-component interaction items; and element 23: element 16 and wherein the at least one interaction term for the fourth FL formula is 3 to 15 interaction terms. Examples of combinations include, but are not limited to, combinations of element 1 and one or more of elements 2 through 22; a combination of elements 2 and 3; a combination of elements 4 and 5; a combination of two or more of elements 2 to 8; a combination of two or more of elements 9 to 15; a combination of one or more of elements 2 to 8 with one or more of elements 9 to 15; a combination of element 16 and one or more of elements 17 through 23; a combination of one or more of elements 2 to 8 with element 16 and optionally a further combination of one or more of elements 17 to 23; combination of one or more of elements 9 to 15 with element 16 and optionally with one of elements 17 to 23 Further combinations of one or more and optionally with one or more of elements 2 to 8.
A fifth non-limiting embodiment of the present invention method comprises: reacting a feed stream 112 comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes; cooling the crude vinyl acetate stream 118 in a heat exchanger 120; the crude vinyl acetate stream 118 is separated into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146; a portion of the flash gas stream 144 is sent to an ethylene recovery process 166 having a vent stream 168; the following conditions were measured: the pressure of the exhaust stream 168, the temperature of the exhaust stream 168, and the concentration of at least one component of the exhaust stream 168, wherein the conditions are at a minimum value (AFL) near the flammability limit min ) And a Flammability Limit (FL) equation including at least one interaction term; oxygen content ([ O) in the exhaust stream 168 is measured 2 ]) The method comprises the steps of carrying out a first treatment on the surface of the And when AFL is used for vent stream 168 returned to ethylene recovery process 166 min ＞FL-[O 2 ]When true, the operating conditions of the ethylene recovery process 166 are changed to AFL min ≤FL-[O 2 ]. The fifth non-limiting example method may further comprise one or more of the following: element 24: wherein the FL formula is according to equation 1; element 25: wherein the at least one interaction item is selected from: a component-component interaction item, a temperature-component interaction item, a pressure-temperature interaction item, and any combination thereof; element 26: wherein the FL formula includes at least two component-component interaction terms; element 27: wherein the FL formula includes at least one pressure-component item, at least one temperature-component interaction item, a pressure-temperature interaction item, and at least two component-component interaction items; and element 28: wherein the at least one interaction item is 3 to 15 interaction items.
Examples of preferred or representative embodiments are given throughout the specification for a better understanding of embodiments of the invention. These examples should in no way be construed as limiting or restricting the scope of the invention.
Examples
Non-limiting examples of how the different FL formulas can be derived are described below.
The general formula for FL is equation 1.
FL＝α+βP+γT+∑δ i [C i ]+∑ε j I j Equation 1
Factors alpha, beta, gamma, delta i And epsilon j The value of (2) may be determined experimentally. Typically, experimentally determining such factors includes setting a reasonable range of potential operating conditions for the location of the FL formulation application.
The maximum oxygen concentration (mole percent of oxygen relative to the total gas) prior to flammability was then experimentally determined under a number of conditions within the range of operating conditions. Based on the collected data, any data fitting model is used to derive the FL formula. A plurality of equations for fitting the data can be obtained. A single equation derived from the data fitting model may have any of the i and j values for equation 1. The values of I and j and their C and I terms in a single equation may be set by the operator prior to data fitting. Alternatively, the values of I and j and their C and I terms in the equation may come from the data fitting model itself. Statistical analysis of the multiple equations may be used to determine which equation to use in operation.
In a first example, a range of potential operating conditions according to table 1 was analyzed with respect to reactor conditions and reactor inlet compositions. To the extent possible, the concentration limit of oxygen flammability was determined in accordance with ASTM E918-09 (2015).
TABLE 1
Temperature (. Degree. C.) 135-190
Pressure (psig) 130-205
Acetic acid (wt%, in oxygen-free gas) 20-40
Water (wt%, in oxygen-free gas) 0-3.2
Methane (mol%, in an oxygen-free dry gas) 0-40
Ethane (mol%, in oxygen-free dry gas) 0-40
Ethylene (mol%, in an oxygen-free drying gas) 35-75
Carbon dioxide (mol%, in oxygen-free dry gas) 0-25
Nitrogen plus argon (mol% in an oxygen-free dry gas) 2-15
A number of FL formulas including equations 7 to 10 are derived, wherein FL is the combustible oxygen composition in the dry gas, mol%; p is pressure, psig; t is the temperature, DEG C; [ C 2 H 6 ]、[CH 4 ]And [ CO ] 2 ]Is the concentration of ethane, methane and carbon dioxide in the oxygen-free dry gas, in mol%; [ HAc ]]Acetic acid concentration in oxygen-free gas, unit weight; [ H ] 2 O]Is the concentration of water in the oxygen-free gas, unit weight; dryingThe gas is a combination of the combined feed stream 112, except for water and acetic acid; the oxygen-free drying gas is a combination of the combined feed stream 112, except for water, acetic acid, and oxygen; and an oxygen-free gas is a combination of the combined feed stream 112, except for oxygen.
Equation 7:
FL＝17.70-0.01487*P-0.0260*T+0.1960*[C 2 H 6 ]+0.0780*[CH 4 ]+0.0805*[C0 2 ]-0.265*[HAc]+2.211*[H 2 O]-0.000168*T*T-0.1467*[H 2 O]*[H 2 O]-0.000127*T*[C 2 H 6 ]-0.000190*T*[CO 2 ]+0.002369*T*[HAc]-0.02035*T*[H 2 O]-0.000327*P*[C 2 H 6 ]-0.000139*P*[CH 4 ]+0.00198*[C 2 H 6 ]*[H 2 O]+0.001097*[CO 2 ]*[HAc]+0.0609*[HAc]*[H 2 O]
equation 8:
FL＝10.05-0.0125*P-0.0015*T+0.2143*[C 2 H 6 ]+0.1482*[CH 4 ]+0.0296*[CO 2 ]+0.2980*[HAc]-2.20*[H 2 O]+0.000092*P*P+0.002608*[HAc]*[HAc]-0.000228*T*P-0.000203*T*[C 2 H 6 ]-0.001594*T*[HAc]+0.0264*T*[H 2 O]-0.000183*P*[C 2 H 6 ]+0.000469*[C 2 H 6 ]*[CO 2 ]+0.000920*[C 2 H 6 ]*[HAc]-0.0422*[C 2 H 6 ]*[H 2 O]-0.0594*[CH 4 ]*[H 2 O]+0.001639*[CO 2 ]*[HAc]
equation 9:
FL＝18.22-0.01909*P-0.04743*T+0.15050*[C 2 H 6 ]+0.0505*[CH 4 ]-0.1063*[CO 2 ]+0.0666*[HAc]-0.311*[H 2 O]+0.000186*T*[CH 4 ]+0.00318*T*[H 2 O]-0.000157*P*[C 2 H 6 ]-0.000827*[CH 4 ]*[HAc]+0.00849*[CO 2 ]*[HAc]
equation 10:
FL＝19.59-0.01226*P-0.0516*T-0.210*[C 2 H 6 ]+0.06460*[CH 4 ]-0.0389*[CO 2 ]+0.0643*[HAc]+0.423*[H 2 O]+0.003292*[HAc]*[HAc]-0.000109*T*P+0.00223*T*[C 2 H 6 ]+0.000573*T*[CO 2 ]-0.000698*T*[HAc]+0.000407*P*[HAc]-0.0184*[C 2 H 6 ]*[H 2 O]+0.001654*[CO 2 ]*[HAc]
statistical analysis may be used to determine which FL formula (e.g., equations 7 through 10 or otherwise) to use in operation. Also, equations 7 through 10 provided herein are derived from the data generated by the conditions of table 1 and are specific to the vinyl acetate system/process structure and conditions specified in the corresponding experimental design. Those skilled in the art will recognize that equations 7 through 10 may not necessarily be used with any vinyl acetate process/system. Moreover, those skilled in the art having the benefit of this disclosure will recognize how to measure flammability data points over a range of conditions suitable for different reactors and how to consider vinyl acetate system/process configurations without undue experimentation.
In a second embodiment, a range of potential operating conditions according to table 2 is analyzed, which may be applied to an inter-process heat exchanger and/or a carbon dioxide removal system. To the extent possible, the concentration limit of oxygen flammability was determined in accordance with ASTM E918-09 (2015).
TABLE 2
Temperature (. Degree. C.) 80-190
Pressure (psig) 145-225
Methane (mol%, in an oxygen-free dry gas) 0-45
Ethane (mol%, in oxygen-free dry gas) 0-45
Ethylene (mol%, in an oxygen-free drying gas) 35-75
Carbon dioxide (mol%, in oxygen-free dry gas) 0-30
Nitrogen plus argon (m 0 l) in an oxygen-free dry gas 0-30
A number of FL formulas including equations 11 to 14 are derived, where FL is the combustible oxygen composition in the dry gas, mol%; p is pressure, psig; t is the temperature, DEG C; [ C 2 H 6 ]、[CH 4 ]And [ CO ] 2 ]Is the concentration of ethane, methane and carbon dioxide in the oxygen-free dry gas, in mol%; and the oxygen-free gas is a composition of the stream, except for water, acetic acid and oxygen.
Equation 11:
FL＝16.56-0.0622*P+0.00560*T+0.12947*[C 2 H 6 ]-0.0179*[CH 4 ]-0.0242*[CO 2 ]-0.000080*T*T+0.000123*P*P+0.000736*[CH 4 ]*[CH 4 ]-0.000154*T*[C 2 H 6 ]-0.000123*T*[CH 4 ]-0.000260*T*[CO 2 ]-0.000255*P*[C 2 H 6 ]+0.000212*P*[CO 2 ]+0.001656*[C 2 H 6 ]*[CH 4 ]+0.001724*[C 2 H 6 ]*[CO 2 ]+0.002705*[CH 4 ]*[CO 2 ]
equation 12:
FL＝20.89-0.1031*P-0.04083*T+0.1723*[C 2 H 6 ]+0.08815*[CH 4 ]+0.05032*[CO 2 ]+0.000051*T*T+0.000226*P*P-0.000591*[C 2 H 6 ]*[C 2 H 6 ]+0.000054*T*P-0.000221*P*[C 2 H 6 ]-0.000121*P*[CH 4 ]-0.001156*[C 2 H 6 ]*[CH 4 ]-0.000482*[CH 4 ]*[CO 2 ]
equation 13:
FL＝7.71+0.0486*P-0.03223*T+0.1447*[C 2 H 6 ]+0.0060*[CH 4 ]+0.0466*[CO 2 ]+0.000058*T*T-0.000172*P*P+0.000336*[C 2 H 6 ]*[C 2 H 6 ]+0.000637*[CO 2 ]*[CO 2 ]-0.000188*T*[C 2 H 6 ]-0.000257*P*[C 2 H 6 ]+0.000127*P*[CH 4 ]-0.000151*P*[CO 2 ]+0.000668*[C 2 H 6 ]*[CH 4 ]+0.000366*[C 2 H 6 ]*[CO 2 ]+0.001649*[CH 4 ]*[CO 2 ]
equation 14:
FL＝12.10+0.0098*P-0.02468*T+0.0964*[C 2 H 6 ]-0.0323*[CH 4 ]+0.00221*[CO 2 ]-0.000082*P*P+0.001022*[CH 4 ]*[CH 4 ]+0.000023*T*P-0.000150*T*[C 2 H 6 ]+0.000052*T*[CH 4 ]-0.000171*P*[C 2 H 6 ]+0.002150*[C 2 H 6 ]*[CH 4 ]+0.001784*[C 2 H 6 ]*[CO 2 ]+0.001472*[CH 4 ]*[CO 2 ]
statistical analysis may be used to determine which FL formulas (e.g., equations 11 through 14 or otherwise) to use in operation. Also, equations 11 through 14 provided herein are derived from the data generated by the conditions of table 2 and are specific to the vinyl acetate system/process structure and conditions specified in the corresponding experimental design. Those skilled in the art will recognize that equations 11 through 14 may not necessarily be used with any vinyl acetate process/system. Moreover, those skilled in the art having the benefit of this disclosure will recognize how to measure flammability data points over a range of conditions suitable for different reactors and how to consider vinyl acetate system/process configurations without undue experimentation.
Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth, used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the embodiments of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
One or more exemplary embodiments are presented herein that incorporate the disclosed embodiments of the invention. In the interest of brevity, not all of the features of a physical implementation are described or illustrated in the present application. It will be appreciated that in the development of any such actual embodiment, as in any engineering project, numerous implementation-specific decisions must be made to achieve the developers' goals, such as compliance with system-related, business-related, government-related and other constraints, which will vary from one implementation to another and from one time to another. While a developer's work may be time consuming, such work is routine for those skilled in the art having the benefit of this disclosure.
Although the compositions and methods are described herein in terms of "comprising" different components or steps, the compositions and methods may also be "consisting essentially of" or "consist of" the different components and steps.
The present invention is therefore well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the invention. The invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein and/or any optional element which is not disclosed herein. Although the compositions and methods are described in terms of "comprising," "including," or "comprising" various components or steps, the compositions and methods may also be "consisting essentially of" or "consist of" the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number falling within the range and any included range are specifically disclosed. In particular, each range value disclosed herein ("about a to about b", or equivalently "substantially a to b", or equivalently "form of about a to b") is understood to set forth each number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Furthermore, the indefinite articles "a" or "an" as used in the claims are defined herein to mean one or more than one of the element to which it is introduced.

Claims (28)

1. A process for producing vinyl acetate comprising:
reacting a feed stream 112 comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes;
cooling the crude vinyl acetate stream 118 in a heat exchanger 120;
separating the crude vinyl acetate stream 118 into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146, wherein the tail gas stream 130 comprises ethylene, carbon dioxide, alkanes, and oxygen, wherein the flash gas stream 144 comprises ethylene, carbon dioxide, alkanes, and oxygen, and wherein the vinyl acetate stream 146 comprises vinyl acetate, water, and acetic acid;
heating the tail gas stream 130 in the heat exchanger 120;
at least a portion of the carbon dioxide is removed from the flash gas stream 144,to produce CO 2 Removing overhead distillation stream 158;
vaporized acetic acid is combined with heated tail gas stream 130 and CO in vaporizer 106 2 Removing overhead stream 158 to be combined to produce vaporized stream 108;
adding oxygen to the vaporized stream 108 to produce the feed stream 112;
measuring and/or determining the conditions according to (a), (b) and/or (c):
(a) The pressure of the feed stream 112 and/or the reactor 116, the temperature of the feed stream 112 and/or the reactor 116, and the concentration of at least one component in the feed stream 112 and/or the reactor 116;
(b) The pressure of the heated tail gas stream 130, the temperature of the heated tail gas stream 130, and the concentration of at least one component of the heated tail gas stream 130;
(c) The CO 2 The pressure of top distillation stream 158 is removed and the CO 2 The temperature of top distillation stream 158 is removed, and the CO 2 Removing the concentration of at least one component in top distillation stream 158; and
wherein (a) there is an association between a first minimum value that is close to the flammability limit and a first flammability limit formula, based on the condition of (a), wherein (b) there is an association between a second minimum value that is close to the flammability limit and a second flammability limit formula, based on the condition of (b), wherein (c) there is an association between a third minimum value that is close to the flammability limit and a third flammability limit formula, based on the condition of (c), wherein one or more of the first flammability limit formula, the second flammability limit formula, and the third flammability limit formula includes at least one interaction item;
measuring and/or determining the oxygen content of a stream selected from the group consisting of: the feed stream 112, the heated tail gas stream 130, the CO 2 Removing overhead distillation stream 158 and any combination thereof; and
when for one or more of (a), (b) or (c) the minimum value close to the flammability limit > flammability limit-oxygen content is true, then a shutdown procedure or corrective step is initiated.
2. The method according to claim 1, wherein the minimum value of the first close to flammability limit is different from the minimum value of the second close to flammability limit and/or the minimum value of the first close to flammability limit is different from the minimum value of the third close to flammability limit and/or the minimum value of the second close to flammability limit is different from the minimum value of the third close to flammability limit.
3. The method according to claim 1 or 2, wherein the first flammability limit formula is different from the second flammability limit formula and/or the first flammability limit formula is different from the third flammability limit formula and/or the second flammability limit formula is different from the third flammability limit formula.
4. The method according to claim 1 or 2, wherein the at least one interaction item is selected from the group consisting of: component-component interaction terms, temperature-component interaction terms, pressure-temperature interaction terms, and any combination thereof.
5. The method of claim 1 or 2, wherein the first, second, and/or third flammability limit formulas comprise one or more items selected from the group consisting of: constant, temperature, pressure, concentration of components in the corresponding composition.
6. The method according to claim 1 or 2, wherein the first and/or second and/or third flammability limit formula comprises at least two component-component interaction terms.
7. The method according to claim 1 or 2, wherein the first and/or second and/or third flammability limit formulas comprise at least one pressure-component item, at least one temperature-component interaction item, a pressure-temperature interaction item, and at least two component-component interaction items.
8. The method according to claim 1 or 2, wherein the at least one interaction-item is 3 to 15 interaction-items.
9. The method of claim 1 or 2, further comprising: a portion of the tail gas stream 130 is combined with the flash gas stream 144 prior to removing at least a portion of the carbon dioxide from the flash gas stream 144.
10. The method of claim 1 or 2, wherein separating the crude vinyl acetate stream 118 comprises:
the crude vinyl acetate stream 118 is separated in separator 122 into a top distillate stream 124 and a first bottom stream 126;
the overhead stream 124 is separated in a scrubber 128 into a tail gas stream 130 and a second bottom stream 132;
first and second bottom streams 126, 132 are combined; and
the combined first and second bottoms streams 126, 132 are separated in a crude drum 142 into the flash gas stream 144 and the vinyl acetate stream 146.
11. The method of claim 1 or 2, further comprising: the vinyl acetate stream 146 is purified to a purified vinyl acetate product stream 150.
12. The method of claim 1 or 2, further comprising:
purifying the vinyl acetate stream 146 into a purified vinyl acetate product stream 150 and one or more additional streams; and
at least one of the additional streams is recycled back to the evaporator 106, the tail gas stream 130 and/or the flash gas stream 144.
13. The method of claim 1 or 2, further comprising: ethylene and/or methane is added to the tail gas stream 130 upstream of the heat exchanger 120.
14. The method of claim 1 or 2, further comprising: at least a portion of the carbon dioxide is removed from the tail gas stream 130 upstream of the heat exchanger 120.
15. The method of claim 1 or 2, further comprising: ethylene and/or acetic acid is added to the evaporator 106.
16. The method of claim 1 or 2, further comprising:
a portion of the flash gas stream 144 is passed to an ethylene recovery process 166 having a vent stream 168;
the following conditions were measured: the pressure of the vent stream 168, the temperature of the vent stream 168, and the concentration of at least one component in the vent stream 168, wherein the condition has a correlation between a fourth minimum value near a flammability limit and a fourth flammability limit equation including at least one interaction term;
measuring the oxygen content in the vent stream 168; and
when the minimum value near flammability limit > flammability limit-oxygen content is true for the vent stream 168 returning to the ethylene recovery process 166, the operating conditions of the ethylene recovery process 166 are changed to a minimum value near flammability limit.ltoreq.flammability limit-oxygen content.
17. The method according to claim 16, wherein the fourth minimum value close to the flammability limit is different from the first minimum value close to the flammability limit and/or the second minimum value close to the flammability limit and/or the third minimum value close to the flammability limit.
18. The method of claim 16, wherein the fourth flammability limit formula is different from the first and/or second and/or third flammability limit formulas.
19. The method of claim 16, wherein the at least one interaction term for the fourth flammability limit formula is selected from the group consisting of: component-component interaction terms, temperature-component interaction terms, pressure-temperature interaction terms, and any combination thereof.
20. The method of claim 16, wherein the first, second, and/or third flammability limit formulas comprise one or more items selected from the group consisting of: constant, temperature, pressure, concentration of components in the corresponding composition.
21. The method of claim 16, wherein the fourth flammability limit formula includes at least two component-component interaction terms.
22. The method of claim 16, wherein the fourth flammability limit formula includes at least one pressure-component item, at least one temperature-component interaction item, a pressure-temperature interaction item, and at least two component-component interaction items.
23. The method of claim 16, wherein the at least one interaction term for the fourth flammability limit formula is 3 to 15 interaction terms.
24. A process for producing vinyl acetate comprising:
reacting a feed stream 112 comprising acetic acid, ethylene, oxygen, carbon dioxide, alkanes, and water in a reactor 116 to produce a crude vinyl acetate stream 118 comprising vinyl acetate, acetic acid, water, ethylene, carbon dioxide, and alkanes;
the crude vinyl acetate stream 118 is cooled in heat exchanger 120;
the crude vinyl acetate stream 118 is separated into a tail gas stream 130, a flash gas stream 144, and a vinyl acetate stream 146;
a portion of the flash gas stream 144 is passed to an ethylene recovery process 166 having a vent stream 168;
the following conditions were measured: the pressure of the vent stream 168, the temperature of the vent stream 168 and the concentration of at least one component in the vent stream 168, wherein the condition has a correlation between a minimum value near a flammability limit and a flammability limit formula including at least one interaction term;
measuring the oxygen content in the vent stream 168; and
when the minimum value near flammability limit > flammability limit-oxygen content is true for the vent stream 168 returning to the ethylene recovery process 166, the operating conditions of the ethylene recovery process 166 are changed to a minimum value near flammability limit.ltoreq.flammability limit-oxygen content.
25. The method according to claim 24, wherein the at least one interaction item is selected from the group consisting of: component-component interaction terms, temperature-component interaction terms, pressure-temperature interaction terms, and any combination thereof.
26. The method according to claim 24 or 25, wherein the flammability limit formula includes at least two component-component interaction terms.
27. The method according to claim 24 or 25, wherein the flammability limit formula includes at least one pressure-component item, at least one temperature-component interaction item, a pressure-temperature interaction item, and at least two component-component interaction items.
28. The method according to claim 24 or 25, wherein the at least one interaction-item is 3 to 15 interaction-items.
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